This invention relates generally to a steering system and, more particularly, to a closed circuit, hydraulic steering system for mobile vehicles.
Hydraulic steering units typically consist of an open-circuit pump that provides hydraulic pressure to a steering unit. The steering unit, in turn, actuates one or more steering cylinders, which control the steering of a vehicle. In some conventional designs, the open-circuit pump is dedicated completely to the steering system and provides full pressure to the steering unit. In such a design, the steering unit distributes the hydraulic fluid flow to the steering cylinders. In other conventional designs, the open-circuit pump is used for several hydraulic systems and includes a priority valve to divert flow to the steering system.
One disadvantage of conventional hydraulic steering units is their large physical size. Because of the need for an open-circuit pump, which utilizes a reservoir, and because of the linear configuration of the steering system, conventional steering units take up a considerable amount of space.
Another disadvantage of conventional hydraulic steering units is that they tend to operate at relatively high pressure levels. Typically, open-circuit pumps deliver about 1800 liters per minute of hydraulic fluid to the steering system at a pressure between 200–250 bar. This high pressure level is necessary for the open-circuit pump to drive the steering system. Such a high pressure level, however, results in substantial noise during operation.
It is therefore a principal object of this invention to provide a hydraulic steering system that occupies a minimum amount of space.
A further object of this invention is to provide a hydraulic steering system that requires a minimum amount of hydraulic pressure for operation.
Still another object of this invention is to provide a hydraulic steering system that operates with a minimum amount of operational noise.
These and other objects will be apparent to those skilled in the art.